There have been proposed many methods of speeding up or slowing down the rate of reproduction of recorded speech. It has also been desired to avoid the change in pitch that accompanies the simple speeding up or slowing down of playback of a conventional analog tape recording.
Storage of speech in the form of digital samples has led to a number of proposals that utilize digital signal processing techniques for time-scale modification. Among these are Cox et al., "Real-Time Implementation of Time Domain Harmonic Scaling of Speech for Rate Modification and Coding", IEEE Transactions on Acoustics, Speech, and Signal Processing, Vol. ASSP-31, No. 1, pp. 258-271, February, 1983; U.S. Pat. No. 4,864,620, issued to Bialick; Malah, "Time-Domain Algorithms for Harmonic Bandwidth Reduction and Time Scaling of Speech Signals", IEEE Transactions on Acoustics, Speech, and Signal Processing, Vol. ASSP-27, No. 2, pp. 121-133, April 1979; U.S. Pat. No. 3,104,284, issued to French et al.; Neuberg, "A Simple Pitch-Dependent Algorithm For High-Quality Speech Rate Changing" (abstract), Journal of the Acoustical Society of America 61, Suppl. 1 (1977). However, the neet has remained for time-scale modification that provides tetter quality reproduction and/or more efficient processing, use of memory, and so forth.